In the World of the High Tech Redneck, the Graybeard is the old guy who earned his gray by making all the mistakes, and tries to keep the young 'uns from repeating them. Silicon Graybeard is my term for an old hardware engineer; a circuit designer. The focus of this blog is on doing things, from radio to home machine shops and making all kinds of things, along with comments from a retired radio engineer running from tech or science news to economics; from firearms to the world at large.

Monday, August 8, 2016

Suddenly Woodworking

I'm pretty sure that every piece I've talked about working on for my G0704 CNC conversion project has been metal. For at least a little while, that has to change. Before I take the mill apart and rebuild it with the pieces I've been making, I've got a lot of stuff to do.

Even if you're not familiar with power tools, it really shouldn't be mysterious that if you start with a block of metal and make it into something smaller, the stuff you cut away has to go somewhere, right? If you cut a cubic inch of metal away, it becomes a cubic inch of waste that needs to be swept or vacuumed up! You may not realize that cutting can throw chips long distances. When I cut the
central bores in my motor mounts, I went up to a 3/4" end mill from a 1/2" diameter cutter, and it
would throw thick, long, curly strings of metal a few feet across the room. It became a habit to make a pass or two with the mill, then vacuum like crazy. Long stringy chips tend to catch in the shop vac hose and make a plug, so I sweep them up. Still, I regularly find small chips and slivers that should be in the vacuum 10' away from the mill - whether they were thrown or stuck to my shoes, I can't say.

An enclosure for the mill will help with clean up and help keep the rest of the shop clean, so I've been studying mill enclosures on YouTube, and a couple of machinist forums since Saturday. A bonus of the enclosure is that it makes flood cooling possible. I've used the Grizzly at low enough cut rates that things haven't gotten too hot - and I've backed off when they have. With the system open to the world, I can use a little oil or some sort of cutting fluid, but only a drop at a time, or very light spray, otherwise the walls, other machines, papers, and yours truly get splattered (DAMHIK, as they say). With an enclosure, it's possible to put a sink drain in a low spot, with some filtering, so that you can flood cool the part and wash the chips into your bucket, filtering out the cooling solution to recirculate. If you buy a commercial CNC system, they offer enclosures as either standard equipment or an option. Take this Tormach PCNC 1100, something a small business would buy. Or a hobbyist wanting to get started making parts and not making his machine.

I've been studying ways to do this since Saturday, and there are some pretty impressive home made systems out there (a collection of photos). I've settled on an approach like the seller of the DVD plans I'm working from has done. It's different than the system on the DVD, but he's posted the new version to one of machinist forums, along with lots of videos. I've spent a couple of hours drawing it in the CAD program, bought some wood, and I'm ready to start cutting the pieces. Painting and sealing is mandatory - and has to be completed by the time I'm taking the mill apart and rebuilding it, so it's a high priority project.

In addition to doing this, I've got to build up my CNC controller box. I have the stepper motor controllers, steppers, and I think I have everything I need, although I may be short of simple stuff like Cat 5 cable. I even think I sketched a schematic at some point, or glommed together a few different pieces of schematic that I found. The controller box needs to be running before I assemble the mill. How can I tell if one my axes binds if I can't drive the motor to make sure? Being a largely electrical job, this is going to be more like working on my home turf. Then there's a computer. I need to build, fix or completely resurrect a computer to run the motion control software.

While the mill is apart, I'll be adding a system to pump a little oil into a handful of places: ballscrews, and where metals slide over each other. I have the oil fittings, or at least some of them, but there are parts I need to get on order for that task. Yeah, I've been trying to read up on how people do that, too. When the mill is being reassembled, there's
stuff to be added and wired into place besides the stepper motors: limit
switches, power to the cooling and oiling systems. And probably things I'm forgetting.

That's actually all that I have planned now. When these things are done, sometime in the next few months, I'll have a CNC'ed, 1HP mill. It should make finishing an AR lower an afternoon job, instead of a couple of weeks like my first one. I hope it ends up having all been worth it. There are other popular mods for the system: ways to run the spindle faster, including a higher power motor for the spindle, and automatic tool changers. I can't say I'm really going to do any of those, but having a tool changer is a BIG step up from doing everything one tool at a time. Higher power is a like a bigger machine. You always want higher power, just like you always seem to need a machine a couple of inches bigger in some dimension than what you have. At some point you have to live with it.

This is how I spend my weekend afternoons and evenings. Studying these questions. How about you?

7 comments:

I remember my father showing me a lathe tool and mentioning a "chip breaker" that was ground into the tool to prevent the long strings of swarf. I cannot remember the details.

I saw a tshirt once that stated, "Sawdust is Glitter for Men." I am sure that swarf falls into the same category. Or as my wife has said after glancing at the upstairs rugs, "Machining aluminum are we?"

I don't think I've seen end mills with chip breakers. In this case, I was using the EM as an oversized drill bit, to get the hole ready for the boring head. Drill bits are famous for generating long, stringy chips, too.

I'm probably a bit more paranoid about aluminum chips because of the cats. I'd hate for one of them to get a chip in a paw. When I get a chip in a finger I either pull it out with a tweezers, or occasionally cut it out with a utility knife. That would be difficult at best with the cats. I'd probably end up needing stitches. Or $1000 at the animal emergency clinic.

The floor in the shop is painted but poured concrete with fiberglass (?) threads sticking out of it, so it's uncomfortable enough that I never walk around barefoot out there. The cats, on the other hand, insist on walking around barefoot all the time.

80/20 makes good stuff. We used a ton of it at Sea Launch to rebuild our equipment consoles after the vendor we called in for a quote to redo them wanted an insane amount of money because "It's on a ship, you know and Marine Stuff costs more">

For your CNC enclosure, consider how you would work on a long object such as a guitar or rifle which doesn't fit inside the box. May I propose a liquidtight bottom tray, but with sides that sit inside that tray so they can be removed without leaving corner columns in the way.

The plans I'm working to are a fixed wood chip tray, 64x36, and the walls of the enclosure are panels that are completely removable. The side panels can be removed by themselves, or the front and sides. 80/20 extrusions, as Dr.Jim says, will be the structural parts, and the pieces will be held in place with suitcase latches.

I really don't envision needing to take the walls down. With a 5 foot wide chip wide tray it's already able to handle pretty big things, but I'll be able to take off either end if I need to.

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Retired radio engineer, follower of Christ, RF designer, mentor. Radio ham, home shop machinist, lapidary, silversmith, roadie cyclist, learning to be a rifleman, and home defender, - a guy with too many interests to keep track of.

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